The present invention relates to a hitch for an agricultural tractor and in particular to a draft link having a recessed pocket on the inboard side thereof and a rotatable wedge shaped bumper that can be moved in the pocket to make adjustments in the amount of permitted sway and/or to compensate for wear of the tractor sway blocks and bumper.
An agricultural tractor is a vehicle intended primarily for off-road usage, designed and advertised primarily to supply power to agricultural implements. An agricultural tractor propels itself, provides a force in the direction of travel and provides mechanical, hydraulic and/or electrical power to agricultural implements to enable them to perform their intended functions. A three-point hitch at the rear of an agricultural tractor is commonly used to couple an implement to the tractor to provide the force necessary to move the implement.
The two lower links in a three-point hitch are known as draft links. The draft links are coupled to the tractor through a ball joint at the forward end of each draft link. The ball joints allow the links to be raised and lowered by pivoting vertically about the ball joints and to sway laterally by pivoting left and right about the ball joints. When the draft links are coupled to an implement, both links must move laterally with one another. This lateral movement, or sway, is limited by engagement of the inboard surface of each draft link with a sway block on the side of the tractor frame. Bumpers or pads are commonly fixed to the inboard side of the draft link to contact the sway block on the tractor frame. A separate bumper provides the ability to make adjustments in the amount of sway permitted, as well as to compensate for wear of the engaging components. In addition, bumpers of different sizes can be used to provide a different draft link end spacing for different hitch categories.
Bumpers that are tapered lengthwise of the draft link are known and shown in U.S. Pat. No. 4,470,613. There the bumper is tapered lengthwise of the draft link. The bumper position is adjustable lengthwise of the draft links to permit minor adjustments in the draft link end spacing and to compensate for wear between the bumper and the sway block.
The draft link of the present invention has a recessed pocket on the inside surface thereof. The recessed pocket has a convex back wall surface which is curved about a center of curvature. A bumper is disposed in the pocket and has a concave inner surface complementary to the convex back wall surface of the pocket. The bumper extends from the pocket and terminates in a convex outer surface. The convex outer surface of the bumper is eccentric to the convex back wall surface of the pocket. As a result, the bumper is wedge shaped, with at least a portion of the convex outer surface extending beyond the pocket, for contact with a sway block on the tractor frame. The bumper is shorter in the longitudinal direction of the draft link than the pocket, allowing the bumper to be rotated in the pocket, about the center of curvature. The position of the bumper in the pocket determines the extent to which the eccentric outer surface projects from the pocket. This determines the amount of lateral sway of the draft link.